Manhole ventilator



p R. DOYLE 3,401,869

MANHOLE VENTILATOR Filed Sept. 19, 196 6 2 Sheets-Sheet 1 BY Robert L. Doyle Attorneys Sept. 17, 1968 R- DOYLE MANHOLE VENTILATOR 2 Sheets-Sheet 2 Filed Sept. 19, 1966 mfm INVENTOR.

Robert L. Doyle BY Attorneys United States Patent 3,401,869 MANHOLE VENTILATOR Robert L. Doyle, Palo Alto, Calif., assignor to Western Progress, Inc., Palo Alto, Calif., a corporation of Nevada Filed Sept. 19, 1966, Ser. No. 580,246 8 Claims. (Cl. 230-117) ABSTRACT OF THE DISCLOSURE Manhole ventilator for moving air relative to a manhole having a housing with front and rear openings and a flow passage extending therethrough, the housing having front end portions, a generally cylindrical portion adjoining the front end portion, a tapered portion adjoining the cylindrical portion and a rear portion adjoining the tapered portion with an axial flow fan disposed in the cylindrical portion and motor means mounted in the housing for driving the fan with straightening vanes mounted within the housing and serving to support the motor means.

This invention relates to a ventilator and more particularly to a ventilator for ventilating manholes.

Heretofore, it has been the practice to ventilate manholes with blowers of the squirrel-cage type. Conventionally, these blowers have been operated by gasoline-powered motors which drive the same. Such units have been found to be relatively heavy and expensive. There is, therefore, a need for a new and improved manhole ventilator.

In general, it is an object of the present invention to provide a manhole ventilator which overcomes the above named disadvantages.

Another object of the invention is to provide a manhole ventilator of the above character which is relatively compact and light and can be readily moved about by one man.

Another object of the invention is to provide a manhole ventilator of the above character which can be powered by a relatively small electric motor.

Another object of the invention is to provide a manhole ventilator of the above character which can be operated from a conventional automobile battery.

Another object of the invention is to provide a manhole ventilator of the above character which can readily overcome the static pressure which is built up in the hose utilized for ventilating the manhole.

Additional objects and features of the above invention will appear from the following description in which the preferred embodiment is set forth in detail in conjunction with the accompanying drawings.

Referring to the drawings:

FIGURE 1 is a perspective view of a manhole ventilator incorporating the present invention being utilized for ventilating a manhole.

FIGURE 2 is a side elevational view of the manhole ventilator shown in FIGURE 1.

FIGURE 3 is a front elevational view of the manhole ventilator.

FIGURE 4 is a cross-sectional view of the manhole ventilator particularly showing the construction of the axial flow fan.

FIGURE 5 is a view looking along the line 5-5 of FIGURE 4 particularly showing the configuration of one of the fan blades.

In general, the present manhole ventilator consists of a housing which has front and rear openings therein and with a flow passage extending therethrough between the 3,401,869 Patented Sept. 17, 1968 front and rear openings. An axial flow fan is disposed within the housing and is provided for moving air through the flow passage. Motor means in the form of an electric motor is disposed in the housing and carries the fan and serves to drive the fan. Means is provided for supporting the motor means within the housing and includes straightening vanes which are secured to the housing and which are secured to the motor means. The vanes, in addition to serving to straighten the air flow, serve as heat radiators for the motor. An elongate flexible hose is mounted on one end of the housing and carries air to or from the housing.

More particularly as shown in the drawings, the manhole ventilator consists of a housing 11 which is formed by a main body section 12 and a front section 13. The body section 12 is provided with a cylindrical portion 12a, a rearwardly and inwardly tapered portion 12b and a cylindrical portion 12c which is of a diameter slightly less than the diameter of the portion 12a. The front section 13 consists of a cylindrical portion 13a and an outwardly and inwardly inclined portion 13b and a generally cylindrical section 130 having a diameter substantially less than the diameter of the portion 13a. The diameters of the portions 130 and 120 are substantially identical. The from section 13 is secured to the body section 12 by suitable means such as screws 16 which secure the portion 13a of the front section 13 to the portion 12a of the body section 12. A guard screen retaining ring 17 is mounted within the portion 13a of the front section 13 and is also secured within the portion 13a by the screws 16. A circular guard screen 18 is disposed within an annular groove 19 provided in the retaining ring so that the retaining ring serves to retain the guard screen across the front section 13.

Thus, it can be seen from FIGURE 2 that the housing 11 is provided with a front opening 21 in the front section 13 and a rear opening 22 in the body section 12 with a Venturi-like flow passage 23 formed between the front and rear openings 21 and 22.

An axial flow fan 26 is disposed within the housing 11 in the portion 12a of the body section 12. The fan 26 consists of a hub 27 which is formed with a hollow cylindrical portion 27a that is open to the rear and a front circular portion 27b that closes the front portion of the cylindrical portion to provide a cup-shaped hub. The hub is also provided with a rounded surface or corner 270 which joins the substantially planar circular portion 27 b with the cylindrical portion 27a. A plurality of radially extending blades 28 are mounted on the hub. As shown in FIGURE 4, eight of such blades are provided and have a particular construction. Each of the blades is provided with straight inwardly tapered side edges 29 in an outward direction and a slightly curved outer edge 31. Each of the blades is of a semi-air foil design. In other words, the pushing side 32 of the blade is substantially planar, whereas the rear side 33 has a convex or air foil design. The fan 26 can be constructed of any suitable material such as diecast aluminum.

Motive means is provided for driving the axial flow fan 26 and for supporting the same and consists of an electric motor 36 which is provided with an output shaft 37. The hub 27 of the fan is secured to the shaft 37 by a set screw 38. The electric motor 36 can be of any suitable type. However, it is preferable that the electric motor be as small as possible while still being sufficiently large to drive the fan to produce the necessary air flow as hereinafter described. In particular applications for which the manhole ventilator is used, it is desirable that the motor be of a type which can be operated from an automobile battery or, alternatively, from a conventional volt A-C source.

Means is provided for supporting the motor 36 within the housing and consists of a cylindrical cage 41 which is secured about the motor 36 by bolts 42, as shown particularly in FIGURE 2. A plurality of radially extending straightening vanes 43 have their inner extremities secured to the cage 41 by suitable means such as welding and have outer angle portions 43a which are secured to the body section 12 of housing 11 by suitable means such as pop rivets 44. In the embodiment shown, six of such straightening vanes have been provided.

As hereinafter described, the straightening vanes 43 have a dual purpose. First, they serve to straighten the air flow from the fan 26, or in other words, remove the swirling action of the air as it comes from the fan; and secondly, they serve as heat dissipators for the electric motor 36. They serve as particularly effective heat dissipators in conjunction with the cage 41 because they are connected directly to the cage 41 and to the body section 12 so that heat can pass directly from the motor 36 to the vanes 43 which are cooled rapidly by the air passing over the same from the fan.

In order to enhance the cooling of the motor, the motor is preferably enclosed in aluminum casting which is a relatively good conductor of heat to rapidly conduct heat to the cage 41 and the vanes 43 which are also preferably formed of aluminum to enhance their heat dissipating abilities. It also is to be noted that the cage 41 and the vanes 43 have a length which is substantially identical to the length of the motor 36 to provide the greatest possible cooling for the motor 36. An electric cord 46 is provided for supplying suitable electric power to the motor 36.

A U-shaped stand 48 is provided for carrying the housing 11 and has its upper extremities secured to the opposite sides of the housing 11 by suitable means such as pop rivets 49. A space 51 is provided below the housing 11 and within the stand 48 which can be utilized for storing the cord 46. Rubber bumpers or feet 52 are secured to the bottom of the stand 48. A carrying handle 53 is secured to the housing by suitable means such as rivets 54. A flexible elongate hose 56 is secured to the rear end of the housing 11 and is utilized for carrying air from the housing 11 into a manhole 57 from which the manhole cover 58 has been removed. Alternatively, if desired, the hose 56 can be mounted on the front end of the housing 11 so that air can be pulled from the manhole rather than pushed down into the manhole. A protective stanchion 61 carrying warning flags 62 is provided to prevent individuals from accidentally falling into the manhole 57.

Operation and use of the manhole ventilator may now be briefly described as follows. Let it be assumed that the manhole ventilator has been positioned in the manner shown in FIGURE 1 and that the hose has been placed in the manhole 57 and that the cord 46 has been connected to a suitable source of power. Thus, if a llO-volt motor 36 is provided, the cord would be connected to a 110-volt source such as one supplied by a motor generator set. Alternatively, if the motor 36 is a conventional 12-volt motor, the cord 46 can be connected to an outlet provided in a motor vehicle and which is connected to the electrical system of the vehicle.

It has been found that with either source of power, namely 12 volts D-C or 110 volts A-C, either type of motor is driven at approximately 3500 rpm. to drive the axial flow fan 26 at the same rate of speed. This causes air to be brought into the front opening 21 into the fan, and then through the straightening vanes 43 and the Venturi-like passage formed by the section 12 out through the rear opening 22 and into the flexible hose 56 and down into the manhole to push air in the manhole out of the manhole. It has been found that the axial flow fan utilized in the manhole ventilator is particularly effective for overcoming the static pressure which is built up in the long length of hose 56. By way of example, it has been found that it is necessary for the fan to generate sufficient air pressure to overcome a static air pressure in the hose equivalent to approximately 4 of an inch of water.

By way of example, it has been found that by utilizing a motor having a /s HP rating, it is possible to deliver approximately 500 cu. ft. per minute through the end of the hose 56 and into the manhole 57 without any undue difficulty and without causing an undue temperature rise in the motor. In this example, the motor had a length of approximately 5 inches and a diameter of approximately 3% inches. The housing 12 had an interior dimension at the fan of 8% inches; the fan had a diameter of 8 inches; and the inlet or from opening 21 and outlet or rear opening 22 had diameters of approximately 7 inches. In such an embodiment, it was found that it was possible to readily deliver 500 cu. ft. of air per minute through 15 ft. of flexible hose having a diameter of 7 /2 inches. Without the hose, it was found that the ventilator could readily deliver 750 cu. ft. per minute.

Thus, it has been found that this relatively light, cornpact manhole ventilator can be used for adequately ventilating manholes. In addition, the ventilator is light enough so that it can be readily carried about by one man. By way of example, one embodiment of the invention had a weight of 17 lbs. The ventilator is also of such a construction that the power consumption is relatively low in comparison to the volume of air which is moved.

I claim:

1. In a manhole ventilator (for moving air relative to a manhole, a housing having front and rear openings therein and a flow passage extending therethrough between the front and rear openings, said housing having a front end portion, a generally cylindrical portion adjoining said front end portion, a tapered portion adjoining said cylindrical portion and a rear portion adjoining the said tapered portion, said front and rear portions being smaller than said cylindrical and tapered portions, an axial flow fan disposed in said cylindrical portion of said housing for moving air through the flow passage in the downstream direction, motor means disposed in said tapered portion of said housing and carrying said fan and serving to drive said fan, said motor means being generally cylindrical in shape throughout its entire length, and said tapered portion being tapered from the fan to the end of the motor means in a direction to cause a substantial portion of said flow passage to have a decreasing cross section in a downstream direction, means including straightening vanes disposed in said housing and secured to said housing and to said motor means, said straightening vanes serving to straighten the air flow from said fan and also serving as heat radiators for said motor means.

2. A ventilator as in claim 1 together with an elongate flexible hose mounted on one end of said housing, said hose being adapted to be inserted into said manhole.

3. A ventilator as in claim 1 wherein said axial flow fan includes a hub and a plurality of blades mounted on said hub at a substantial angle with respect to the axis of rotation of said hub, each of said blades having straight tapered side edges which are tapered inwardly in an outward direction, each of said blades having an air pushing side and a rear side, said air pushing sidebeing substantially planar and said rear side being substantially convex.

4. A ventilator as in claim 3 wherein each of said blades is formed of solid metal.

5. A ventilator as in claim 3 wherein said hub has a size in cross section along a plane perpendicular to the axis of rotation of the hub which is substantially the same as the corresponding cross section of the motor means.

.6. A ventilator as in claim 1 together with a stand secured to said housing for supporting said housing, said stand being substantially U-shaped with a bottom wall spaced a substantial distance from the housing to provide a storage space between the bottom wall and the housing, said motor means including a cord for supplying power to said motor means, said storage space being capable of receiving said cord for storage.

7. A ventilator as in claim 1 together with a guard screen mounted in said housing in front of said fan.

5 6 8. A ventilator as in claim 1 wherein said means includ- References Cited ing straightening vanes includes a cage mounted on said UNITED STATES PATENTS motor means and secured to said vanes, said cage being constructed so that the motor means is removable from 2394517 2/1946 Ingans 230-120 said cage. 5 HENRY F. RADUAZO, Primary Examiner. 

